Electrical discharge device



June 13, 1944. H. H. RACE ELECTRICAL DISCHARGE DEVICE Filed May 2, 1942 Fig/1f. A

@y ma t?. r C I@ t. vrt 2% Ib E IL/H w C a Patented June 13, 1944 1 ELECTRICAL DISCHARGE DEVICE Hubert H. Race, Schenectady, N. Y., assigner to General Electric Company, a corporation of New York Application May 2, 1942, serial No. 441,501

(o1. 31a-32s) 7 Claims.

My invention relates to spark plugs.

An object of my invention is to provide an improved spark plug having a construction which minimizes the possibility offlashmver within the plug by substantially eliminating gas electrical discharge paths between the distribution lead and the shell of the plug.

Further objects and advantages of my invention will become apparent and my invention will be better understood fron; the following description referring to the accompanying drawing, and the features of novelty which "characterize my invention will be pointed out. wlthllparticularity in the claims annexed to and forming part of this specification. f

In the drawing, Fig. 1 is an elevational view, partly in section, of a spark plug and a distribution lead provided with an embodiment of my invention; Fig. 2 is an enlarged sectional view of the upper portion of the spark plug and its connection to the distribution lead shown in Fig. 1; Fig. 3 is a modication of the construction shown in Figs. 1 and 2; Fig. 4-is an enlarged view of the resilient bushing and non-deformable cap shown in Fig. 3; land Fig. 5 is a modication of the bushing and cap shown in Figs. 3 and 4. L

Referring to the drawing, I have shown a spark plug provided with an outer metallic sleeve or barrel ID and threaded at one end II for engagement with a complementary threaded opening in an engine block and having an enlarged portion I2 adapted to be engaged by a wrench or similar tool. Grounding electrodes I3 are secured to the shell I adjacent the lower threaded end Il and a central or dischargeelectrode I4 is supported within the spark plug-by a ceramic insulating core I5 of porcelain or similar material. The discharge electrode I4 is formed with a lower flange I6 which engages a complementary shoulder Il on the insualting core I5 and is provided with a turnedv-over contact -head portion I8 which secures a cap I9 in position over a c en trai opening 20 in the insulating core I5. This central opening 20 in the core I5 between the electrode flange I6 andthe cap I8 is filled with a body 0f compressed or compacted powder. The core l5 is held in positionin theshell I0 by en.- gagement adjacent its lower end with a Vgasket 2| seated on a shoulder 22 formedon the shell II) and by engagement at the'opposite end there.. of with a turned-over end 23 of the shell I0.

The desired electrical potential is .brought to the central electrode I4 by a distribution lead 24 oi electrically conductive material which is 55 insulated by a suitable exible insulating covering 25 about which an armored metallic shield 28 is arranged. The distribution leadis held in position on the spark plug by a terminal elbow 2l which is secured to the head of the spark plug shell I0 by a threaded nut 28 provided with an annular ilange'29 which extends over a complementary flange 30 on the elbow 28 and secures the elbow flange 30 against a heat resistant bushing 3| of deformable resilient material such asa high molecular weight polybutene ory a mixture of polystyrene with polyisobutylene which is prepared as the composition described in British Patent No. 513,630 (1939), which is arranged. between the flange 30 and the upper end 23 ofy the shell I0. These are all resiliently held together by the threaded engagement of the nut 28 with threads 32 formed on the adjacent upper end oi the spark plug shell I0. In order to assure good electrical contact between the spark plug central electrode I4 and the distribution lead 24, a terminal connector is provided which includes an electrically conductive bushing 33 having a cen trai passage 34 formed therein through which an end of the distribution lead 24 is threaded and is securely held by spreading the outer ends of the conductors of the lead 24 over the end'of the bushing 33. This bushing is held in position in an insulating sleeve element 35 of relatively non-deformable material such as ber and is securely anchored thereto by an annular flange 36 which is molded in the sleeve 35 and which extends into a complementary groove formed on the outer peripheral surface of the bushing l33.

A contact comprising a coil spring 3l is arranged over the end of the bushing 33 and extends from the adjacent end oi' the insulating sleeve 35 into contact with the upper adjacent end of the central discharge electrode I4.

Under certain atmospheric conditions, such as relatively low pressure, there is a tendency for the voltage to discharge from the lead to the grounded plug shell through any gas discharge path. In order substantially to eliminate corona discharges and arc-over between the spark plug III and the electrical connection of the distribution lead 24 with the central discharge electrode I4, I provide a heat resistant bushing 38 of de formable resilient insulating material like bush ing 3| arranged within the shell between the end 23 of the shell and the electrical connection of the lead 24 with the discharge electrode I4 within the insulating element l5. This deformable bushing is pressed into deformed position by enH gagement of the lower end of the terminal mem- `ber insulating'sleeve 35 -forl substantially fillingI a circumferential portion of vthe space aboutthe f lead connection andfsealing the spacebetween the lower end yof theterminal 'member'an'dthe shell; thereby substantiallyy eliminating free openrv gas electrical discharge'paths ibetween the lead and' the shell. When this bushingfisrdeformedfinthis manner; a part of the 'upper portion thereof' extends upwardlyl around the.` insulating I sleeve 35i about'the" lead 'l 24=and1fseals the air space between the lead connection andthe upper'resilient" bushing. 3l, thereby-f effectively minimizingA the tendency toward` corona discharges through the' air space between .the leadconnection4 and' the upper end of-the shell. The'two bushingsv 3l and n aresecurelyv held. in their deformed-positions'by tighteningv the nut 28'on the upperend of the shell I I0, asthis biasestherelbow 2"A into tight engagement, with the upper' portion of thebushingv 3landiwith'thefupper end .of the insulating sleeve 35, thereby biasing thisV sleeve into tight. engagement with 'the upper end of the' bushing 33?.'

A modification of this construction vis shown in Fig. 3 wherein the discharge portion of the'sparky plugis formed ofsub'stantially the same elements asthose shown in Figs.' land 2v and includes a vdischarge. electrode Il' arranged-1n the central opening of an insulating element. lof'fceramic material'securedfwithinxthe spark plug shell l0v` and retained in positionthereinby the upper turned-over end 23" of the shell l0; In this isprovided withjaa. V-'section lwedge end portion 4l' which engages'y thev Vupper endrof the deformable resilient'bushing 43A andextendsinto a complementary` V-grove 45' in thel upper end of the desire itto bee-understood,` therefore, that my inctmstruction, the distribution lead 24 andv its surrounding insulation: 25. extendsfintothe spark plug shell |05- and.` is providedwith a; terminal' washer 39 of electrically conductive .material se-A cured to the turned-'over ends of' the distribution lead 2l. The distribution lead. "is electrically connected with the central discharge electrode I l by a coilspringlof electric-:ally con-- ductivematerlal. In this construction, `the ilange..

Il of the terminalelbow-'N is arranged in en'- gagement with-a relatively nondeformable capv element M of insulating material andy withtlie complementary il'ange 29 formedfl on thevupper.-

end of the threaded nut 28 which threadedly engages the upper end' ofl the: spark plug shell ,IIL The cap 40 is providedl with an inwardly tapered Wedge-shaped lower portion-4| arranged in engagement with a complementary Wedgeshaped upper portion 420i a neat resistant bush'- ing formed of deformable resilient insulating material like bushing- 3l. This bushing 43 is ar- A. ranged about' the leacl12'4 andv its insulation 25 within the shell l0 between the electricalv con-` nection oi' the lead' 24to the electrode Il and' ventionfisnot'to 'be limited tothe particular arrangements. disclosed, and I intend in the appended claims to cover all modiilcations which do notv depart'fromithe spirit and scope vof vmy invention. jf'

WhatI'claimf-as new and desire to secure by Letters Patentfof" Vthe UnitedStates is:

l. A sparklplug including a shell having a grounding electrode, a discharge electrode arranged withinsaid shell, means including an insulating 'elementi arranged about a part of said discharge electrode inl said shell for supporting said electrode, ifa-'lead` ofrconductive material electrically connected to said discharge electrode within said f insulating element, aheatl resistant bushing Ofdeiormable yresilient insulating material arranged within said' insulating element. rbetween said shellrlandsaid lelectrical connection of said'lead to said discharge-electrode, and means including ar-relatively non-deformable insulating element'arrangedv about said lead in engagement ,withv said deformable bushing. deforming saidbushingzfor substantially nlling a portion of the space about said lead connection for eliminating free-open gas electricaldlscharge paths between said lead and said shell.

2. 'A spark lplug including a` shell having a grounding electrode, a dischargel electrode arrangedwithin' said shell, an insulating element the upper end of the shellv l0. When thenut.-

284s secured'in position; it draws. the flange 30 of the terminal elbow 21 downwardly into engagement withthe upper engi' of the'cap 40 which compresses anddeforms the-bushing 43v and substantially circumferentiallyflls a longitudinal portion of the spaceV about. the lead within the shell between the terminalfwasher 39 and the upper end oi' the shell, therebyveliminating-l free open gas electrical discharge paths between the shell and the lead, thus ellectively. sealing the space between'. the shell' and. the terminal connection 39 similar-to the pair of bushings inthe construction shownv in Figs. l and 2. 'The de- Iormable' resilient bushing ,43 and' relatively nondeformable cap -Illfare shown inv detailinFig. 4.

This deformable bushing and relativelyv non'- deformable vcap construction vmaybe formed with a. double conical AWedge vengaging lsurface as shown arranged between a part off` said discharge elec` trode and'saidmshell, a lead of conductive materialelectrically'connectedto said discharge elec- ,1 trode within said shell; a heat resistant bushing of deformableiinsulating*material arranged between said shell and said electrical connection of said lead tor-said discharge electrode,` means including relatively non-deformable insulating element arranged in engagement with said de-` formable. bushing deforming said bushing for substantially filling a portion of the space about said lead connection for eliminating free open gas electrical discharge paths between said lead connection and said shell, a second deformable insulating bushing arrangedv between said shell and said insulating element, and means deforming said second bushing for sealing the space between said shell and said rst-mentioned bushing. l

3. A spark :plug includingl ashell having a groundingv electrode,v a discharge electrode arranged within said shell, an insulating element arrangedbetween a part of said discharge electrode and said shell, a lead of conductive material electrically connected to said' discharge electrode within said shell, insulation arranged about said lead and extending within said shell about a portion of said lead, a heatV resistant bushing olv defonnable insulating material` arranged between said shell and said electrical inl Fig.4 5' wherein the non-deformablecap, 40-

substantially filling a portion of the space about said lead connection for eliminating free open gas electrical discharge paths between said lead and said shell, a second deformable insulating bushing arranged between said shell and said lead insulation, and means deforrning said second `bushing for sealing the space between said shell and said first-mentioned bushing.

4. A spark plug including a shell having a grounding electrode, a discharge electrode arranged within said shell, an insulating element arranged between a part of said discharge electrode and said shell, a distribution lead of conductive material electrically connected to said discharge electrode within said shell, insulation arranged about said lead and extending within said shell about a portion of said lead, a heat resistant bushing of deformable insulating material arranged between said shell and said electrical connection of said lead to said discharge electrode, means including a relatively non-deformable terminal member arranged in engagement with said deformable bushing deforming said bushing for substantially filling a portion of the space about said lead connection and sealing the space between one end of said terminal member and said shell for eliminating free open gas electrical discharge paths between said lead and said shell, a second deformable bushing of resilient insulating material arranged between said shell and said terminal member, and means deforming said second bushing for sealing the space about said terminal member between said shell and said first-mentioned bushing at the other end of said terminal member.

5. A spark plug including a shell having a grounding electrode, a discharge electrode arranged within said shell, an insulating element arranged between a part of said discharge electrode and said shell, a distribution lead of conductive material electrically connected to said discharge electrode within said shell, a heat resistant bushing of deformable resilient insulating material arranged between said shell and said electrical connection of said lead to said discharge electrode, means including a relatively non-deformable terminal member extending about a portion of saidlead and arranged in engagement with said deformable bushing deforming said bushing for substantially sealing the space between one end of said terminal member and saidshell for eliminating free open gas electrical discharge paths between said lead and 'said shell, a second deformable bushing of resilient insulating material arranged between said shell and said terminal member, and means deforming said second bushing for sealing the space about said terminal member between said shell and said first-mentioned bushing at the other end of said terminal member.

6. A spark plug including a shell having a grounding electrode, a discharge electrode arranged within said shell, an insulating element arranged between a part of said discharge electrode and said shell, a distribution lead of conductive material electrically connected to said discharge electrode within said shell, a heat resistant bushing of deformable resilient insulating material arranged within said shell about a portion of said lead, and means including a relatively non-deformable element having a wedgeshaped portion arranged in engagement and extending within an end of said deformable bushing for deforming said bushing providing good contact ibetween said bushing and the adiact surfaces on each side thereof and substantially filling a longitudinal portion of the space almut said lead Within said shell eliminating free upon gas electrical discharge paths between said .shell and said lead.

7. A spark plug including a shell having a grounding electrode, a discharge electrode arranged within said shell, an insulating element arranged between a part of said discharge electrode and said shell, a distribution lead of conductive material electrically connected to said discharge electrode within said shell, a heat resistant bushing of deformable resilient insulating material arranged within said shell about a portion of said lead, and means including a relatively non-deformable element having a wedgeshaped portion arranged in engagement with said deformable bushing for deforming said bushing and substantially filling a coaxial portion of the space about said lead within said shell eliminating free open gas electrical discharge paths between said shell and said lead.

HUBERT H. RACE. 

